When you found CMOS checksum error message this indicates that your CMOS battery is weak or dead. You have to replace with the new one.
Replacing CMOS battery will need to open computer casing so you need to prepare screwdriver and a new CR 2032 battery.
Beside CMOS checksum error message it will also reset all your BIOS setting thus every time you turn on the computer it will ask setup BIOS before you can continue working with the computer, this is very annoying.
If you don't replace the battery there is a possibility that the batter will swell and will produce a liquid that will ruin motherboard and make further damage.